Ok, this one has been vexing me, the neighbors and the plumbers and I'm
hoping someone can help.

My house was built in 2000 and over the last 4 or 5 months I have
noticed an increasingly strong odor when filling the tub or the washing
machine or any area where a large amount of the water collects. Now
then I'm noticing it when flushing the toilets and even from some of
the faucets. The odor is not sulphur, not bleach, not sewer, not
earthy smell (I've smelled all of these things in water before). The
best I can explain it is that it is a semi-sharp, chemically smell,
very distinct, but nothing I've smelled before. I am on city water and
I've had three neighbors on either side over to smell it and no one can
place it. They haven't had the problem and I've gone to 2 different
houses to run water just to verify and there is absolutely no odor.

The smell is only there when running the water, both hot and cold. I
have run the water into a plastic basin only to eliminate the
possibility that it is coming out of the drain when the water runs in.
The strange thing is that the smell dissapates after 5 minutes or so;
it's as if it is a some type of gas venting out of the pipes. Taking a
cup of the water away immediately from the source and the water doesn't
smell or taste funny at all and the color is fine.

I tried turning off the main valve and opening several faucets, tub,
etc. and then turned it back on and let it all run for 15 minutes or
so. It then didn't smell (that I could notice) for almost 24 hours.
It does seem to be much less when a large amount of water has been run;
again, almost as if it's venting some smelly gas from the pipes.

Call to the city and they said no one has complained (confirmed by
neighbors). Brought out the plumber and he was stumped. He'd never
smelled the smell before. He checked the meter and it wasn't running
so he didn't think there were any leaks. He called the office and the
head guy swore it was the hot water heater. He said mine had an
aluminum anode and I should replace with magnesium (which now that I
read some posts seems backwards).

Anyway, now I have a new hot water heater and the smell was back in a
day. I'm waiting to hear back from them and see if he is going to give
me 95% of his paycheck he was willing to bet that day (I'm guessing
no).

I'm at a complete loss here and everyone I talked to, has no idea and
it is starting to worry me. Anyone have any idea on this one. Your
help is greatly appreciated.

Thank you.